I have a kohler whirlpool in my co-op apartment installed by privious owner.When tub is filled more than half way and drained, it causes dirty water to backflow into my neighbor's bathtub.

A plumber who looked at the problem thinks it's a clog somewhere in the drain.

The management thinks that it's because of a lack of VACUUM BREAKER (which they described as a hole on the wall outside of the tub).He wants me to restore the drain to a 'normal' drain because the current one is causing vapor lock.

Does this make any sense?It doesn't to me so far... but I'm pretty new at this.